The present invention relates to graphene and more specifically, to one, few, or multi-layer graphene synthesis wherein the graphene is continuous over macroscopic areas (e.g., areas greater than 20 by 20 microns square) and uniform in thickness.
The exceptionally high intrinsic carrier mobility of graphene makes it a potentially promising material for high frequency electronic devices such as low-noise amplifiers for communication applications. The term “graphene” as used herein denotes a one-atom-thick planar sheet of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. Graphene can be comprised of single-layer graphene (nominally 0.34 nm thick), few-layer graphene (2-10 graphene layers), multi-layer graphene (greater than 10 graphene layers), a mixture of single-layer, few-layer, and multi-layer graphene, or any combination of graphene layers mixed with amorphous carbon (a-C) and/or disordered carbon phases. A disordered carbon phase may be, for example, a crystalline carbon phase with a high density of defects or a nanocrystalline carbon material. Existing methods to prepare the required single-layer or few-layer graphene are far from ideal for commercial use. Graphene from mechanical exfoliation of graphite provides a good quality material, but the yield is low and the inspection requirements are daunting. Graphene layers prepared by thermal treatments of single crystal SiC layers can provide large areas of graphene, but processing is difficult (given the requirements for temperatures in excess of 1100° C.-1200° C.) and the SiC template crystals are expensive and limited in size. Chemical vapor deposition (CVD) methods, in which carbon from a carbon-containing gas is dissolved into the surface of a metal layer at high temperature at about 900° C. to 1000° C. and then converted into surface layers of graphene, also exist. While CVD methods have progressed substantially over the past year, it is still nontrivial to produce few-layer graphene that is continuous over macroscopic areas and uniform in thickness. Once a graphene layer is formed on a substrate, the layer would typically be transferred to another substrate for further use.